Inner table with general title

I have table like this

first second third

How can i do this table , with 2-level hierarchy or more /

header
first second third

I have one idea : MoveTo current Cell ,Add New Cell , and add this lower cells(first,second,third ) and header cell (header) in this. This is what i want to result.

Hi Ilya,

Thanks for your inquiry. Please see attached sample input/output Word documents and following code to achieve this requirement.

Document doc = new Document(MyDir + @"in.docx");
Table tab = (Table)doc.GetChildNodes(NodeType.Table, true)[0];
Row clone = (Row)tab.FirstRow.Clone(true);
tab.Rows.Add(clone);
foreach (Cell cell in tab.FirstRow)
{
    cell.RemoveAllChildren();
    if (cell.IsFirstCell)
    {
        cell.CellFormat.HorizontalMerge = CellMerge.First;
        cell.Paragraphs.Add(new Paragraph(doc));
        cell.FirstParagraph.ParagraphFormat.Alignment = ParagraphAlignment.Center;
        cell.FirstParagraph.Runs.Add(new Run(doc, "header"));
    }
    else
    {
        cell.CellFormat.HorizontalMerge = CellMerge.Previous;
    }
}
doc.Save(MyDir + @"15.8.0.doc");

Hope, this helps.

Best regards,